The mediators of hypersensitivity and inflammation generated by cellular enzymatic pathways of lipoxygenation of arachidonic acid have been defined structurally and in terms of their potent effects on human airway smooth muscles, blood vessels, epithelial cells, glands, nerves, phagocytic leukocytes, and T-lymphocytes. The research proposed will focus on the central biochemical and cellular events critical to the activation and regulation of expression of specific lipoxygenases and related cellular enzymes. The physician-scientist training of the principal investigator will begin with a broad education (Phase I) in the chemistry and immunochemistry of eicosanoids and other fatty acids, the cell biology and enzymology of the lipoxygenation of fatty acids, the differentiation and functions of enzymes, receptors and other cellular structures, and the molecular genetics and biochemistry of biological macromolecules. The concepts and laboratory methods assimilated then will be applied by the principal investigator in a program of research (Phase II) designed to elucidate the characteristics of development of lipoxygenases and epoxide hydrolases in the course of differentiation of cultured human and animal mast cells and eosinophils. The products of lipoxygenation of arachidonic acid will be identified and quantified by chromatographic, spectrometric, and radioimmunochemical techniques in studies of the time-course, cellular properties, and specific stimuli of the development of lipoxygenases and epoxide hydrolases. The 5-lipoxygenase and 5,6-epoxide hydrolase of mast cells and the 15-lipoxygenase and 14,15-epoxide hydrolase of eosinophils will be purified and the catalytic activities, specificity, and susceptibility of the purified enzymes to natural and pharmacological modulation will be defined. A biologically relevant lipoxygenase will be selected for purification in quantities sufficient for determinations of structural and molecular genetic properties. The elucidation of the cellular and chemical bases for development and activation of the pathways of lipoxygenation of arachidonic acid will lead to more reliable assays for detection of abnormalities in the pathways in defective host defense and in immunological diseases and to the development of more specific agents for effective treatment of such disorders.